Final answer:
The correct description of diminishing recency effect is that performance of an unrelated task after memorizing an item list will decrease the number of items recalled toward the end of the list.
Step-by-step explanation:
The correct description of diminishing recency effect is option 3) Performance of an unrelated task after memorizing an item list will decrease the number of items recalled toward the end of the list.
Diminishing recency effect refers to the decreased ability to recall items that were presented toward the end of a list after performing an unrelated task. This effect occurs because the performance of the unrelated task interferes with the ability to remember the most recent information in short-term memory.